From Zelda Legends Wiki
|| Appearance: LA (DX)|
Order: Shadow Nightmare
Habitat: Windfish's Egg
Quick Facts: Agahnim’s Shadow is a replica of Agahnim in battle, he now only looks bigger
Attack Pattern: Same as Agahnim (in ALttP)
Agahnim’s Shadow is the second of the six final bosses you have to beat in LA (DX). In the plot of the game these six Nightmares are responsible for the problems on Koholint Island; simply put their destruction means your victory. Inside the Wind Fish’s Egg you will confront him just after beating the Shadow Gel.
Anybody who still knows Agahnim from ALttP will find it relatively easy to beat him, because he uses an identical attack pattern. Agahnim will pop up somewhere and create a ball of light. As soon as he fires it you must return it to him using your sword to reflect it. But be careful for he can create an almost identical ball that cannot be reflected back. Instead this one will break into six smaller ones that will fly across the room. These however can be deflected by using you sword again, so you won’t get hit. He also has a teleporting ability, but he only uses it to move to a different spot in the room.
His appearance is different from ALttP. In that game Agahnim was a lot smaller and didn’t have these oddly shaped fingers. The only addition in the GB Color version is the color of its’ eyes have changed.
All Nightmares in the Egg except for Dethl are (bigger) copies from enemies in this / or previous Zelda games.
Note that the game itself never gives names to the Nightmare shadow forms. The names are taken from the official NOA guide. Thus, it could be argued that this is not actually Agahnim's Shadow, but merely a shadow that looks like Agahnim. The usual interpretation, however, is that the Shadow forms arise from Link's subconscious. This would mean that the Ganon and Agahnim forms are memories from Link's previous adventures, either in ALttP or in the Oracle games. Although the last thing would be impossible for certain technical reasons...
After entering the shadow’s lair you get a message from all of them:
We were born of nightmares... To take over this world, we made the Wind Fish sleep endlessly! If the Wind Fish doesn't wake up, this island will never disappear! We would have been the masters of this place... But you had to come here and disrupt our plans! Heh heh! You can never defeat us!!! Let's rumble!
need to be done